Micro Electro-Mechanical Systems (MEMS), such as motion sensors and movable mirrors, are being widely used. As is well known, a MEMS motion sensor may be, for example, an accelerometer for detecting linear motion, or a gyroscope for detecting rotation and angular velocity.
Advanced planar silicon processes are being increasingly used to manufacture MEMS devices. Glass frit bonding has been used for wafer-level packaging of MEMS devices, such as accelerometers. However, due to its limitation in achievable minimum seal width, cost, and lead content, a substantial number of the current generation of gyroscopes are made using other wafer-level packaging solutions, such as eutectic solder bonding.
To be effective, a eutectic wafer bonding processes require clean surfaces. Excessive amounts of native oxides and other organic contaminants on the surfaces may damage surface bond formation, strength, and integrity. Depending on the materials in the seal layer stack and device configurations, the removal of the native oxide layer and other contaminants from the surface being bonded may cause difficulties. Robust wafer bonding and sealing of MEMS devices using eutectic wafer bonding processes continues to pose challenges.